Inn is a place that provides accommodation and food for travellers. An Inn provides guest with a place to sleep. It is located in country side and highway while a guest house is a private house that is offered for accommodation to a paying guest. A guest house is a small house close to a bigger one.
If you plan on staying in a foreign land for sometime it is best to stay in a guest house because it is cheap. As the name suggest, a guest house is like living as a guest in someone's house. The guest house has a setting of a typical house. Usually, it has a sitting room, kitchen, bedroom and other relevant space in a house.